They only began to tank when it was mathmatically obvious that they had no shot at making the play in. It was after they blew a big lead in a game against the Hornets late in the season that Luka sat and the Mavs went full tank the last few games of the season. Do you see anyone claiming they'll be good without Kyrie and AD out? If you are going to suck, may as well get some assets this year, maximize your odds of getting a good pick while you can and shed some salary while you're at it. Why rush Kyrie and AD back for what is going to be a bad year anyway? If you can get value out of PJ Washington or Gafford and shed some salary sending Klay to a contender, you absolutely do it at this point to begin to get some assets back. Why would you want to be a borderline second apron lotto team? It makes no sense.
You may be the first person I've ever seen complain about Mark Followill. He's one of the best in the NBA..